Biophysical studies are planned on human and porcine neurotubule assembly and disassembly. Kinetics will be characterized in vitro by electron microscopy and optical measurements to ascertain the important factors involved in the control and mechanism of assembly. Assembly and disassembly of paired helical filaments, which have been found only in the abnormal human brain, will be studied using protein isolated from autopsied brain from patients with senile dementia, Alzheimer's disease or Guam-Parkinsonism dementia. Major goals are to understand the echanism of action of colchicine and vinblastine on microtubules, the possible regulatory role of Ca ions, Mg ions and Zn ions on microtubule assembly and the difference between neurotubules and paired helical filaments. BIBLIOGRAPHIC REFERENCES: Gaskin, F. and Gethner, J.S.: Characterization of the invitro assembly of Microtubules. In Cell Proliferation, Volume 3, Cell Motility, ed., R. Goldman, T. Pollard and J. Rosenbaum, Cold Spring Harbor Lab., Cold Spring Harbor, New York pp. 1109-1121, 1976. Fujimoto, G.I., Saldana, L.R. and Gaskin, F.: Uterine Tubulin Production during Early Pregnancy in the Rabbit. Endocrine Res. Comm. 3-219-229 (1976).